Locking mechanism

ABSTRACT

A device for heave compensation of a tool unit that is suspended via one or more wires from a mast mounted on a platform, each wire at a first end being attached to the mast via an attachment and running via a first heave compensation unit, and each wire at a second end being attached to a second heave compensation unit that is connected to the tool unit. The second heave compensation unit includes a movable compensation mechanism, which at its first end is attached to the wire and which at its second end is attached to the tool unit. The second heave compensation unit includes a releasable locking device with which the motions of the compensation mechanism can be selectively prevented and allowed.

The invention relates to well operations, especially in connection withproduction of hydrocarbons from underground formations. Morespecifically, the invention relates to a device for heave compensationof equipment on a moving vessel, as disclosed in the preamble of theindependent claims.

BACKGROUND OF THE INVENTION

During the recovery of hydrocarbons from wells in undergroundformations, the operator must sometimes carry out work in the wells.Such work may be maintenance or other technical operations, such asperforating, replacing or reperforating pipes, changing flow regulators,isolating production zones, monitoring production and logging pressure,flow and temperature. A motivating factor for the work is to increasethe recovery rate of the well. This work, which is referred to by thecollective term ‘well intervention’, is difficult to perform fromconventional surface platforms, especially when subsea wells areinvolved. It is well known that subsea wells are less maintained thanplatform wells and hence have lower recovery rates. It is thereforedesirable to have systems that are suitable for maintenance of subseawells.

A distinction is made between light well intervention and heavy wellintervention. Today, light well intervention is carried out with the aidof wireline operations from a ship. Heavy well intervention (whichincludes the whole spectrum of intervention work) is usually carried outfrom a special moored, semi-submersible rig that is connected to thewells via a riser (pipe for gas and/or liquid). The special rig fillsthe gap between the ordinary drilling rigs and the vessels that carryout light well intervention using wireline operations, and has, interalia, substantially lower costs than an ordinary drilling rig.

To further optimise costs, it is therefore desirable that such specialrigs are of maximum flexibility, such that, for example, in addition tocarrying out heavy well intervention they can also carry out light wellintervention using wireline-operated tools.

Known floating intervention rigs have a drilling machine suspended froma tower via a heave compensation system for compensating for wavemotions, which may comprise a combined hoisting and compensationcylinder. The tower and the cylinder are mounted on deck. In an ordinarydevice, the drilling machine is suspended from wires (so-called drillline), which run over guide pulleys at the top of the mast, viareversing pulleys at the top of the cylinder, to a fixed point at thetop of the mast. The drilling machine can therefore be hoisted up anddown by moving the cylinder, and the cylinder also compensates—withincertain tolerances—for the motions of the rig such that the drillingmachine is kept as steady as possible when carrying out interventionoperations. A combined hoisting and compensation cylinder of this kindis capable of handling large loads, typically in the order of 250tonnes.

This device is used, for example, when landing large weights on theseabed or inside the drilling riser, as well as during drilling, and canbe operated in passive or active compensation mode when there is a needfor greater accuracy and control of the compensation.

The prior art comprises WO 2007/145503 A1, which describes a device anda method for heave compensation. A mast is mounted on a floating vessel,a first compensation means that is attached via wire means on one sideof the mast, and the other end of the wire means is further connected toa second heave compensation means attached to a tool unit for carryingout drilling operations. The second heave compensation means and thetool unit are moved along guide rails in the mast with the aid ofdollies/lever arms.

There are stringent requirements as regards the ability of the wellintervention rig to—very accurately—compensate for the movements of therig. Heave compensation requirements are often concretised as an abilityto compensate weight change, positioning accuracy and speed limitation.In known well intervention rigs, however, the size of the combinedhoisting and compensation cylinder, and the friction in the guidepulleys and reversing pulleys make it difficult to satisfy one or moreof these requirements. There is therefore a need for a device that iscapable of obtaining greater accuracy in heave compensation than is thecase with known well intervention rigs. The invention meets this needand has other advantages in addition.

SUMMARY OF THE INVENTION

Therefore, a device is provided for heave compensation of a tool unitwhich is suspended via one or more wire means in a mast mounted on aplatform, each wire means at a first end being attached to the mast viaan attachment and running via a first heave compensation unit, and eachwire means at its other end being attached to a second heavecompensation unit that is connected to the tool unit, characterised inthat the second heave compensation unit comprises a movable compensationmeans which at its first end is attached to the wire means and which atits second end is attached to the tool unit, and that the second heavecompensation unit comprises a releasable locking means with which themotions of the compensation means can selectively be prevented andallowed.

In an embodiment, the compensation means is attached to the wire meansvia a connecting unit and is attached to the tool unit via a linkelement, the connecting unit and the link element being movable inrelation to one another, and where the locking means is movable forselectively and releasably limiting the motions of the connecting unitand the link element in relation to one another.

In an embodiment, the locking means comprises a locking bolt with acentral, narrowed portion and broad shoulder portions at each end of thebolt.

In an embodiment, the link element comprises a through hole having afirst portion and a second portion, the first portion having a largeropening than the second portion. The first portion has a dimension thatallows passage of the shoulder portions whilst the second portion has adimension that does not allow passage of the shoulder portions, but doesallow passage of the central portion. In an embodiment, the firstportion has a circular cross-section and the second portion is elongate.

In an embodiment, the wire means runs between the second heavecompensation unit and the first heave compensation unit via guidepulleys that are mounted at an upper part of the mast, and run via thefirst heave compensation unit between the guide pulleys and theattachment in the mast.

In an embodiment, the first heave compensation unit is connected at afirst end to the platform and at a second end is movably attached tosaid wire means via reversing pulleys and a cylinder.

In an embodiment, the device comprises locking means with which themovements of the compensation units can selectively be prevented, andthe compensation units transfer loads between the tool unit and the wireunit as substantially rigid bodies.

In an embodiment, the first heave compensation unit functions as anactive heave compensator whilst the second heave compensation unitfunctions as a passive heave compensator.

In an embodiment, the second heave compensation unit is an integral partof the tool unit. The first and second heave compensation units arepreferably hydraulically operated.

The second heave compensation unit can quickly and simply be installedon any drilling machine, without structural modifications of thedrilling machine.

OVERVIEW OF THE FIGURES

These and other characteristic features of the invention will beelucidated in the following description of preferred, non-limitingembodiments, with reference to the accompanying schematic drawings,wherein:

FIG. 1 shows a mast with a compensation system, seen from a side;

FIG. 2 shows a mast with the compensation means according to theinvention, seen from the front;

FIG. 3 shows the mast and the compensation means shown in FIG. 2, butfrom another side;

FIG. 4 a shows a section of a first embodiment of the invention, seenfrom a side, where the cylinders in the second heave compensation unitare in a retracted position;

FIG. 4 b shows the section shown in FIG. 4 a, seen from the front;

FIG. 4 c corresponds to FIG. 4 b, but shows the cylinders in the secondheave compensation unit in a fully extended position;

FIG. 4 d corresponds to FIG. 4 b, but shows the cylinders in the secondheave compensation unit in a mid position;

FIG. 5 a shows a section of a second embodiment of the invention, seenfrom a side, where the cylinder in the second heave compensation unit isin a retracted position;

FIG. 5 b shows the section shown in FIG. 5 a, seen from the front;

FIG. 5 c corresponds to FIG. 5 b, but shows the cylinders in the secondheave compensation unit in a fully extended position;

FIG. 5 d corresponds to FIG. 5 b, but shows the cylinders in the secondheave compensation unit in a mid position;

FIG. 6 a shows a section of a third embodiment of the invention, seenfrom a side, where the cylinder in the second heave compensation unit isin a retracted position;

FIG. 6 b shows the section shown in FIG. 6 a, seen from the front;

FIGS. 7 a and 7 b show the third embodiment of the heave compensationunit in an unlocked state, seen respectively from the front and from aside;

FIGS. 7 c and 7 d are an enlarged section of FIGS. 7 a and 7 brespectively, and FIG. 7 e is a sectional view of that shown in FIG. 7d;

FIGS. 8 a and 8 b shows a locked state, where the motion damper has notbeen activated;

FIGS. 8 c and 8 d are enlarged sections of FIGS. 8 a and 8 brespectively, and FIG. 8 e is a sectional view of that shown in FIG. 8d;

FIGS. 9 a and 9 b show a state in which it is possible to pull thelocking bolt out of the keyhole, and FIG. 9 c is an enlarged sectionalview of that shown in FIG. 9 b; and

FIGS. 10 a and 10 b shows a position for weight reduction by screwingtogether drilling machine and drill string, a so-called “thread-saver”function, and

FIG. 10 c is an enlarged sectional view of that shown in FIG. 10 b.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows a mast 1 located on a deck 2, for example, on anintervention rig or drilling rig (not shown). An active heavecompensation cylinder 7 and accumulator 8 and a combined hoisting andheave compensation cylinder 4 are mounted on the deck 2. The heavecompensation cylinder 4 is equipped at its upper end with reversingpulleys 5 for hoisting wires 6. It is usual to have four or six parallelrunning hoisting wires.

With reference to FIG. 2, the combined hoisting and heave compensationcylinder 4 has a length of stroke d, where the cylinder rod 12 is in afully extended position. The fully retracted and extended positions,respectively, of the reversing pulleys are indicated by the referencenumerals 5 and 5′.

In the illustrated embodiments, the mast is constructed of a latticestructure in a known way, and will therefore not be described in moredetail here. Similarly, the heave compensation units are driven by fluidreservoirs, regulating valves and systems, gas tanks and hydraulic powerunits. These components are well known to the skilled person and aretherefore not referred to in more detail here.

The mast is equipped with guide rails 9 for a drilling machine 11 in aknown way. Furthermore, with reference to FIGS. 2 and 3, the wires 6 areconnected to the upper part of the mast via an anchorage 10. The wires 6run from the anchorage 10 via the reversing pulleys 5 on the cylinderrod 12 of the combined hoisting and heave compensation cylinder 4,onward via guide pulleys 3 at the top of the mast and then down to acompensator 20, which is connected to the drilling machine 11. FIG. 2shows the combined drilling machine 11 and compensator 20 in a lowerposition against the deck 2, whilst these units in FIG. 3 are raisedslightly from the deck.

Three embodiments of the compensator are described below.

First Embodiment

Referring to FIGS. 4 a-d, the compensator 20 comprises two cylinders 22a,b that are directly connected between the drilling machine 11 and theconnecting link 24 of the hoisting wires. The hoisting wires (not shownin FIGS. 4 a-c) are connected to the connecting link 24 via suitableattachments 25. FIG. 4 a further shows a dolly 21 attached to thedrilling machine 11 for engagement with the tower guide rail asdescribed above.

The cylinders 22 a,b are equipped with a lock 23 with which thecylinders can be locked in the retracted position when the system is notin use. The load from the drilling machine 11 is transferred to thelifting wires via the cylinders 22 a,b and the connecting link 24.

FIGS. 4 a,b show the cylinders 22 a,b in a retracted position, FIG. 4 cshows the cylinders 22 a,b in a fully extended position, whilst FIG. 4 dshows the cylinders 22 a,b in a mid position. The reference numeral 26indicates the respective cylinder rods of the cylinders.

Fluid reservoirs and control units for the heave compensation cylinders22 a,b are in accordance with the prior art and are therefore notdiscussed in more detail here.

Second Embodiment

Referring to FIGS. 5 a-d, the compensator 20′ comprises one cylinder 27which is connected between the drilling machine 11 (via a link 29) and aconnecting link 28 for the hoisting wires (only attachments 25 for thewires are shown in FIGS. 5 b-d). FIG. 5 a further shows a dolly 21attached to the drilling machine 11, for engagement with the tower guiderail as described above.

The cylinder 27 is equipped with lock 23 with which the cylinders can belocked in collapsed position when the compensator 20′ is not in use. Theload from the drilling machine 11 is transferred to the hoisting wiresvia the cylinder 27 and the connecting link 28.

The FIGS. 5 a,b show the cylinder 27 in a retracted position, FIG. 5 cshows the cylinder 27 in a fully extended position, whilst FIG. 5 dshows the cylinder 27 in a mid position. The reference numeral 26indicates the cylinder rod of the cylinder. Fluid reservoirs and controlunits for the heave compensation cylinder 27 are in accordance with theprior art and are therefore not discussed in more detail here.

Third Embodiment

With reference to FIGS. 6 a to 10 c, the compensator 20″ comprises onecompensator cylinder 31 (also referred to as a motion damper) that ismounted to a connecting piece 32 for the hoisting wires. FIGS. 6 a and 6b further show a dolly 21 attached to the drilling machine 11, forengagement with the tower guide rail as described above. On theconnecting piece 32 there is mounted a lock 30 (which, for example, ishydraulically operated via an actuator 86) that is capable of connectingtogether the connecting piece 32 and the below-lying link element 33from which the drilling machine 11 is suspended. The lock 30 bears allload when it is in the locked position and the compensator 20″ is not inuse, such that the load from the drilling machine 11 is transferred tothe hoisting wires via the link element 33, the hydraulically operatedlock 30 and the connecting piece 32. FIGS. 6 a,b show such a lockedposition, in which the cylinder 31 is in a retracted position and isinactive. Fluid reservoirs and control units for the compensationcylinder 31 are in accordance with the prior art and are therefore notdiscussed in more detail here.

FIGS. 7 a to 10 c are further illustrations of the compensator cylinder31, the connecting piece 32, the link element 33 and the connectionbetween these components in different configurations.

The connecting piece 32, to which the compensator cylinder 31 and thewires 6 are fastened, comprise two plate elements 32 a,b arranged spacedapart and fastened together by means of upper bolts 81 and lower bolts83. The lock 30, with its hydraulic actuating mechanism, is alsoattached to the connecting piece (hydraulic connecting lines are notshown, as they are prior art). The lock 30 comprises a housing 30′ witha locking bolt 87, a locking bolt cylinder 88 and a position sensor 89for the locking bolt. The locking bolt 87 has a central narrowed portion87 b, and broad portions (flanges) 87 a at each end.

In this illustrated embodiment, the link element 33 also has a plateform, and is disposed between the plate elements 32 a,b of theconnecting piece in such a way as to be movable. The cylinder rod 26 ofthe compensator cylinder 31 (whose housing is fastened to the connectingpiece) is secured to the link element 33 via a fastening bolt 84. Thelink element 33 is provided with a through “keyhole” 82, which isadapted for receiving the locking bolt 87. The keyhole 82 is elongateand has a lower portion 82 a that has a larger opening than theabove-lying, slightly narrower portion 82 b of the keyhole.

The broad end portions 87 a of the locking bolt 87 have across-sectional dimension that allows passage through the lower, broadportion 82 a of the keyhole and into the respective support holes 37 inthe side plates 32 a,b, but does not allow passage through theabove-lying portion 82 b. The central, narrowed portion 87 b of thelocking bolt has a cross-sectional dimension that allows movement of thelocking bolt up and down in the keyhole, also in the slightly narrowerportion 82 b.

FIGS. 7 a-e show an unlocked state. The locking bolt 87 has been fullywithdrawn from the keyhole 82 in the link element 33, thereby allowingthe link element 33 to move between the two side plates 32 a,b in theconnecting piece 32. The link element 33, which is connected to thecompensator cylinder 31 via the cylinder rod 26, can move between alower position (as shown) and an upper position, limited by,respectively, the upper shoulders 85 and lower shoulders 90 and thelower (stop) bolts 83. The figures show that when the link element 33 isin the full lower position, it will rest on the two lower bolts 83 viathe shoulders 85, which will prevent the drilling machine from fallingif the compensator cylinder 31 should fail. When the cylinder stroke isreduced to about half stroke (compared with that shown in FIGS. 7 a-d),the system will be in the position for motion damping.

FIGS. 8 a-e show a locked stated wherein the motion damper 31 is not inuse. The system is locked, such that all load passes through the lockingbolt without affecting the motion damper. The load is suspended from thedrilling machine (not shown) and is transferred to the link element 33.The link element 33 is suspended from the locking bolt 87 that is seatedin holes in the side plates 32 a,b of the connecting piece 32. From thelocking bolt 87, the load passes through these two side plates up to theupper bolts 81, which connect the hoisting wires to the connecting piece32. This is a normal configuration of the suspension system for drillingand lifting/lowering the drill string.

FIGS. 9 a-c show a state in which the lower link element 33 has beenlifted up to a maximum height in the keyhole 82, such that the lockingbolt shoulders 87 a and the broad portion 82 a of the keyhole arealigned with one another. This is the only position in which it ispossible to pull the locking bolt 87 out of the keyhole 82. The lockingbolt is moved (pulled) horizontally by means of a cylinder 88 equippedwith a stroke sensor 89 such that there is control of whether the boltis in lockable engagement with the keyhole or not. This lifting of thelink element 33 is done with the aid of the compensator cylinder 31. Asdescribed above, FIGS. 9 a-c also show that the lower dimension(diameter) of the keyhole is so great that the locking bolt can be movedhorizontally through the keyhole. In the upper, narrower part of thekeyhole, it is not possible to move the locking bolt in a horizontaldirection owing to the shoulders having increased diameter at the ends.However, the locking bolt is free to be moved vertically in the keyhole,throughout the length of the keyhole. The sectional view in FIG. 9 cshows the locking bolt half out of engagement. It can be seen that thelocking bolt has a shoulder 87 a with a larger diameter at both endsthan the diameter of the central portion 87 b. The diameter of theshoulders fits in the supporting holes 37 of the connecting piece 32 andthe lower part 82 a of the keyhole in the link element.

FIGS. 10 a-c shows a state in which the locking bolt 87 is locked, butthe damping cylinder 31 (not shown in FIGS. 10 a-c) is actuated with asmall stroke such that the locking bolt is roughly in the middle of thekeyhole 82. This is a position for weight reduction on screwing togetherthe drilling machine and the drill string, a so-called “thread-saver”function.

The task of the compensator 21″ is to hold tool that has been loweredinto the well in an accurate position without subjecting equipmentinstalled in the well to weights greater than typically ±500 kg whilstthe main heave compensation is in progress with the aid of the combinedhoisting and heave compensation cylinder 4, with associated accumulatortanks and other necessary, known equipment (not shown). The compensator21″ with compensation cylinder 31 takes the “peaks” of the damping fromthe main compensator 4.

The compensator 21″ may thus have at least the following two functions:

-   a) Damping/minimising vertical motion and controlling/minimising    load against components inside the well from tools that may be    lowered down into it; and-   b) Reducing the load between the shaft of the drilling machine and    the top of the drill pipe when they are to be screwed together    (thread-saver).

Although the compensator 21″ is described here as being made up of alower link element 33 that is movably arranged between the two sideplates 32 a,b of the connecting piece 32, the invention should not belimited to such designs, as a variant may be an inverted configurationwhere the lower link element has two side plates and the connectingpiece comprises one element that is movably arranged therebetween. Theinvention should also not be limited to plate-shaped elements.

Features Common to the Embodiments

The combined hoisting and heave compensation cylinder 4 and associatedcomponents (in the following also referred to as Stage 1) are used whenlanding large loads on the seabed or inside the drilling riser, andduring drilling. In such situations, the compensator 20; 20′; 20″ is notnecessarily in use, i.e., the cylinders are locked via their respectivelocking mechanisms 23; 30.

For heave compensation, Stage 1 can be operated in passive compensationmode or in active compensation mode.

In situations where greater accuracy and control of the compensation arerequired, as for example, during well intervention, Stage 1 will beoperated in active compensation mode. Stage 1 will therefore be able toachieve heave compensation down to a certain minimum level.

The compensator 20; 20′; 20″ (in the following also referred to as Stage2) is used together with Stage 1 in order to further increasesensitivity and accuracy, and to ensure that the power of the drillingmachine does not exceed a defined minimum value. Stage 2 then functionsas a passive heave compensator. The compensator in Stage 2, which mayhave a relatively short stroke length, is constructed such that thecylinder piston is held stationary until loaded with a predefinedweight. When such a predefined weight has been reached, the compensatorin Stage 2 will compensate by either retracting or extending thecylinder rod 26.

Examples of situations in which the need for a Stage 2 is presentinclude landing of lighter equipment within the casing and subsea safetyvalves.

A two-stage heave compensator of this kind can thus—veryaccurately—compensate for the motions of the rig. Within givenoperational parameters (e.g., max heave motion of rig), Stage 1 andStage 2 in combination can compensate for a relatively small weightchange and obtain major positioning accuracy at a limited speed. Asmentioned above, a combined hoisting and compensation cylinder cantypically handle loads of the order of 250 tonnes. In such a connection,a relatively small weight change may be of the order of ±500 kg, and thepositioning accuracy can be of the order of ±10 cm.

Stage 1 can handle large loads and most of the heave. The compensator20; 20′; 20″ (Stage 2) is however substantially smaller than Stage 1 andthus generates less packing friction. In addition, the compensator inStage 2 is located on top of the drilling machine 11 such that it doesnot take with it other friction than that in the compensator 20; 20′;20″, and possibly some from the well.

The compensator 20; 20′; 20″ is thus able to reduce the load amplitudefrom Stage 1 to a load oscillation that is within the requirement forweight change compensation.

The device according to the invention functions in this way as atwo-stage heave compensator, where the combined hoisting and heavecompensation cylinder 4 (Stage 1) handles the large loads, whilst thecompensator 20; 20′; 20″ (Stage 2, which has better sensitivity andgreater accuracy) is able to compensate for loads that are smaller thanStage 1 is adapted to compensate for.

In an embodiment, the load for which the compensator 20; 20′; 20″ isdesigned to compensate may be of the order of 8-10% of the load capacityof the hoisting system.

It will be appreciated that the device for heave compensation can beused for purposes other than well intervention.

The numerical values in the description above have been included toillustrate the application of the invention, and should not be regardedas a limitation of the invention.

1. A device for heave compensation of a tool unit that is suspended via one or more wires from a mast mounted on a platform, each wire at a first end being attached to the mast via an attachment and running via a first heave compensation unit, and each wire at a second end being attached to a second heave compensation unit that is connected to the tool unit, wherein the second heave compensation unit comprises a movable compensation mechanism, which at its first end is attached to the one or more wires and which at its second end is attached to the tool unit, and the second heave compensation unit comprises a releasable a locking device with which the motions of the compensation mechanism can be selectively prevented and allowed.
 2. The device as disclosed in claim 1, wherein the compensation mechanism is attached to the one or more wires via a connecting unit and is attached to the tool unit via a link element, and wherein the connecting unit and the link element are movable in relation to one another, and wherein the releasable locking device is movable for selectively and releasably limiting the motions of the connecting unit and the link element in relation to one another.
 3. The device as disclosed in claim 2, wherein the releasable locking device comprises a locking bolt with a central, narrowed portion and broad shoulder portions at each end of the bolt.
 4. The device as disclosed in claim 2, wherein the link element comprises a through hole with a first portion and a second portion, the first portion having a larger opening than the second portion.
 5. The device according to claim 4, wherein the first portion has a dimension that allows passage of the shoulder portions whilst the second portion has a dimension that does not allow passage of the shoulder portions but does allow passage of the central portion.
 6. The device according to claim 4, wherein the first portion has a circular cross section and the second portion is elongate.
 7. The device as disclosed in claim 1, wherein said one or more wires between the second heave compensation unit and the first heave compensation unit runs via guide pulleys which are mounted at an upper portion of the mast, and run via the first heave compensation unit between the guide pulleys and the attachment in the mast.
 8. The device as disclosed in claim 1, wherein the first heave compensation unit is connected at a first end to the platform and at a second end is movably attached to the one or more wires via reversing pulleys and a cylinder.
 9. The device as disclosed in claim 1, comprising a locking mechanism with which the motions of the compensation units can selectively be prevented and the compensation units transfer loads between the tool unit and the one or more wires as substantially rigid bodies.
 10. The device as disclosed in claim 1, wherein the first heave compensation unit functions as an active heave compensator whilst the second heave compensation unit functions as a passive heave compensator.
 11. The device as disclosed in claim 3, wherein the link element comprises a through hole with a first portion and a second portion, the first portion having a larger opening than the second portion.
 12. The device according to claim 5, wherein the first portion has a circular cross section and the second portion is elongate.
 13. The device as disclosed in claim 2, wherein the first heave compensation unit is connected at a first end to the platform and at a second end is movably attached to the one or more wires via reversing pulleys and a cylinder.
 14. The device as disclosed in claim 2, comprising a locking mechanism with which the motions of the compensation unit scan selectively be prevented and the compensation units transfer loads between the tool unit and the one or more wires as substantially rigid bodies.
 15. The device as disclosed in claim 3, comprising a locking mechanism with which the motions of the compensation unit scan selectively be prevented and the compensation units transfer loads between the tool unit and the one or more wires as substantially rigid bodies.
 16. The device as disclosed in claim 4, comprising a locking mechanism with which the motions of the compensation unit scan selectively be prevented and the compensation units transfer loads between the tool unit and the one or more wires as substantially rigid bodies.
 17. The device as disclosed in claim 5, comprising a locking mechanism with which the motions of the compensation unit scan selectively be prevented and the compensation units transfer loads between the tool unit and the one or more wires as substantially rigid bodies.
 18. The device as disclosed in claim 6, comprising a locking mechanism with which the motions of the compensation unit scan selectively be prevented and the compensation units transfer loads between the tool unit and the one or more wires as substantially rigid bodies.
 19. The device as disclosed in claim 7, comprising a locking mechanism with which the motions of the compensation unit scan selectively be prevented and the compensation units transfer loads between the tool unit and the one or more wires as substantially rigid bodies.
 20. The device as disclosed in claim 8, comprising a locking mechanism with which the motions of the compensation unit scan selectively be prevented and the compensation units transfer loads between the tool unit and the one or more wires as substantially rigid bodies. 